Tremolo-vibrato circuitry for use with a simulated moving sound source or the like



April-16, 1968 D. M. PARK 3,378,623

TREMOLO-VIBRATO CIRCUITRY FOR USE WITH A SIMULATED MOVING SOUND SOURCEOR THE LIKE Filed May 7, 1965 2 Sheets-Sheet 1 28 ;-"*""""I 21? LAMP I842 I DRIVER PHASE 46 I SPLIT 0 26 1 9Q LAMP 21 I m i DRIVER I o 4 44 90T T 270 PHAS 3 SHIFT 45, 2 27 T i I (I LAMP 22 I I 40 DRIVER I 0 5 PHASEI av SPLIT 25 A Q LAMP 20 DRIVER I 3 68 38 VARIABLE PHASE SHIFT LQVVFREQUENCY 79 TREMQLQ QSCILLATQR ADDING kFIG 1 OSCILLATOR CQNTRQL CIRCUIT(6 CPS.) 48

I 69/ 67 SYNCI-IRONIZING g6 GENERATOR AND LQVV FREQUENCY AMPLIFIER IOVIBRATQ OSCILLATOR OSCILLATQR (12 CBS.) CONTRQL 141 OSCILLATOR 48SEQUENTIAL L CQNTRQL IMPEDANCE I PHASING gg FFgEQUENCY CONTROLQSCILLATQR (6 CPS/38 VARIABLE FIG 3 I PHASE SHIFT SYNCHRONIZING 66 68CIRCUIT l P'FC'III LOW FREQUENCY 5o VIBRATO I I NVENTOR.

QSCILLATQR I2CPS /69 I Donald M. Park QSCILLATQR '51 TONE GENERATOR Io ICONTROL AND AMPLIFIER fggfig D. M. PARK 3,378,623 TREMOLO-VIBRATOCIRCUITRY FOR USE WITH A SIMULATED April 16, 1968 MOVING SOUND SOURCE ORTHE LIKE 2 Sheets-Sheet :1

Filed May '7, 1965 ATTORNEY R m m hm N w M m h a m w OE om W N JoEzou IAmmo m: $02 368 mOEiGwO 7 02mm; Czwzomfi 303 v 1 Z616 56x6 25Q wwzmiomzu w i Kim wmfii mJm E Amm my mozjomo JoEzou 06355 mi 19,3 58$538K 0J United States Patent TREMOLO-VIBRATO CIRCUITRY FOR USE WETH ASIMULATED MOVING SOUND SOURCE OR THE LIKE Donald M. Park, deceased, lateof Raleigh, NC, by Mary S. Park, executrix, Raleigh, N.C., assignor toThe Seeburg Corporation, Chicago, IlL, a corporation of DelawareContinuation-impart of application Ser. No. 425,353, Jan. 13, 1965. Thisapplication May 7, i965, Ser. No. 454,771

'5 Claims. (Cl. 84-1.18)

This invention is concerned with repetitive sequential connection of aplurality of speakers with a common audio source and a sound sourcephysically moving from point to point along a defined closed path oftravel. The invention is especially useful with musical circuitry forsuccessively and repetitively keying a plurality of physically displacedspeakers for the purpose of adding unique tremolo and vibrato effects tosounds produced by electric organs or the like.

This application is a continuation-in-part of an application entitledSequential Connection of Speakers for Moving Sound Source Simulation orthe Like, Ser. No. 425,353, filed Jan. 13, 1965.

Various mechanical means are employed in electric organs for introducingtremolo or vibrato. Generally, such means are directed to orbitalmovement of a sound source whether in the form of a speaker which isrotated or of an opening of a rotary horn or baffle which registers witha stationary dynamic speaker. In any event, such apparatus is bulky andintroduces heat, electrical, mechanical inertia, rumbling and other wellknown operating and maintenance problems. Furthermore, an analysis ofsounds coming from such apparatus reveals a complex mixture of varyingtremolo, vibrato, Doppler and other effects. The vibrato and tremolocomponents are generally not controllable either individually orindependently. Desired radiation patterns are not easily obtainable.Frequency response and power handling capabilities are limited.

In the previously referred to co-pending application Ser. No. 425,353,there is disclosed a system which simulates by electrical means theeffect of a sound source physically moving in a closed path. In thereferred to system a plurality of speakers are connected in parallel toa tone generator through a single amplifier. A variable impedance, suchas a light sensitive resistor, is placed in the path of each speaker andmeans are provided to sequentially light the impedances to vary theirrespective values according to some predetermined phase relation. Thus,the audio signal originating in the tone generator is sequentiallydirected to the speakers which are physically displaced. With fourspeakers physically displaced ninety physical degrees apart and theimpedances phased ninety electrical degrees apart, for example, the tonesource sounds at if it is physically moving rom speaker to speaker andthere is blending of the speaker tones as the sound moves each ninetydegree step.

The circuitry of the referred to co-pending application discloses bothtremolo or amplitude and vibrato or frequency control of the audiosignals which enter the speakers. That is, the variable impedances, thelight sensitive resistors, are varied in value at a tremolo rate ofabout 6 cycles per second and the rotating effect is at this tremolorate. In addition to varying the mentioned impedances at the tremolorate the sound source is varied in frequency at a vibrato rate of 6cycles per second. The ultimate sound heard by the listener thus is aninteresting and pleasing combination of both tremolo and vibratoeffects.

3,378,623 Patented Apr. 1%, 1968 While the invention of the co-pendingapplication has achieved truly unique sound effects there has beenlacking certain desired qualities when compared to the well known Leslieeffect. Many of these qualities are found in the present invention. Forexample, it has been discovered in the present invention that if thetone source is both frequency modulated and amplitude modulatedsimultaneous with amplitude modulation of the mentioned impedances, newand interesting sounds are produced and which simulate to a high degreethe Leslie effect. It has also been discovered that a difference betweenthe amplitude and frequency modulating frequencies can be employed toimprove the quality of the Leslie effect.

An object of the present invention is therefore to provide an improvedcircuitry and speaker system for simulating a moving source of sound.

A further object is to provide an improved circuitry and speaker systemwhich simulate a moving source of sound without requiring physicalmotion of the source and which exhibits improved tremolo-vibratoquality.

A further object is to provide a circuitry for successively and smoothlykeying at a tremolo rate a plurality of physically displaced speakers toa tone source which is subjected to both vibrato and tremolo modulationsuch that each speaker is connected in turn to the source torealistically simulate a sound moving from speaker to speaker whileexhibiting both tremolo and vibrato effects.

Another object is to provide an improved circuitry and system inelectrical musical instruments or the like for producing vibrato,tremolo and phase shift effects that can be individually controlled.

Another object is to provide an improved sequential keying circuitryutilizing light sources and light sensitive impedances suitable tosequentially keying devices such as speakers in electrical musicalinstruments or the like.

Another object is to provide an improved electronic system forrealistically simulating the tremolo and vibrato effects of a movingsource of sound by means of a plurality of speakers but which requiresonly one power amplifier.

The foregoing and other objects will appear from the followingdescription and drawings, in which:

FIGURE 1 is a block diagram of an electric organ system incorporatingthe invention.

FIGURE 2 is a more detailed combined block and circuit diagram followingthe FIGURE 1 system.

FIGURE 3 is a generalized diagram of an electric organ speaker systemincorporating the invention.

The invention is illustrated in FIGURE 1 in connection with an electricorgan and with a group of four speakers labeled 1, 2, 3 and 4 which itis desired to sequentially and repetitively connect in the same order(that is, 1, 2, 3, 4) to a common sound source identified as an organtone generator-amplifier It That is, the object of the circuitry ofFIGURE 1 is to make the source of sound seem' to rotate by causing it tocome out sequentially and repetitively first from speaker I, thenspeaker 2, then speaker 3, then speaker 4, then speaker I and so forth.The amplitude variation at each speaker is smooth and blends with thelast and next succeeding speaker. The speakers themselves should beunderstood as being physically displaced as illustrated by FIGURE 1 inwhich dashed line 11 schematically represents a suitable speaker cabinetcontaining the respective speakers 1, 2, 3 and 4 physically displacedninety degrees apart around the inside walls of the cabinet. Thephysical displacement of the speakers may of course be at other thanninety degrees to achieve different rotative effects and as will beunderstood from later description there may be more or less than fourspeakers.

Each speaker has a connection with the tone generator and each suchconnection is controlled by a light sensitive impedance. In the exampleof FIGURE 1, the rotating effect is achieved at a tremolo rate, 6 cyclesper second, by varying the value of such an impedance in series witheach speaker preferably sinusoidally and at the tremolo rate. That is,amplitude modulation is applied to each impedance at a tremolo rate. Theimpedances may take the form of light sensitive resistors provided byphoto-conductive tubes 20, 21, 22 and 23 as illustrated by FIGURE 1 and2 and which are connected in series connection respectively withspeakers 1, 2, 3 and 4. Delco type LDR-25 photo-conductor tubes sold byDelco Division, General Motors Corporation, Kokomo, Ind. are suitable.Tubes 20, 21, 22 and 23 are in turn sensitized by corresponding lamps25, 26, 27 and 28 and when illuminated their resistance drops abruptlyfrom a high value to a low value.

The voltages which energize the lamps are derived fro-m correspondinglamp driver circuits 30, 31, 32 and 33. The tubes 20, 21, 22 and 23 andthe lamps 25, 26, 27 and 28 should in any event preferably exhibit shortturn-on and turn-off times to achieve the desired smooth following ofthe sound around its path. The intensity of the type lamp employedshould vary linearly with the voltage across the lamp and the impedanceof the photo conductor tube employed should approximate a linearfunction of the incident light intensity so that the amplitude modulatedtone at the speaker approximates sinusoidal modulation. Furtherreference to use of such variable impedances, namely light sensitiveresistors, to gain musical effects may be found in Patent 3,119,890.

The detailed description thus far has primarily dealt with the subjectmatter of the previously referred to co-pending application Ser. No.425,353. To continue this description as background for the presentinvention it has already been mentioned that the value of theirnpedances provided by tubes 20, 21, 22 and 23 are varied sinusoidallyand at a tremolo rate. This is accomplished by furnishing the lampdrivers 30, 31, 32 and 33 with driving voltages which are sequentiallystepped out of phase by some predetermined electrical phase diiference,a ninety degree phase difference being used. That is, using the voltagedriving lamp driver 30 as a reference such voltage has zero phasedeviation as indicated in FIGURE 1. The voltage driving lamp driver 31is however ninety degrees out of phase with that driving driver 30; thevoltage driving driver 32 is another ninety degrees or one hundred andeighty degrees out of phase with that driving driver 30; the voltagedriving driver 33 is still another ninety degrees or two hundred andseventy degrees out of phase with that driving driver 30.

The described shifting and tremolo rate of energizing lamps 25, 26, 27and 28 and consequent tremolo rate of illuminating tubes 28, 21, 22 and23 is obtained by connecting a suitable, for example voltage controlled,low frequency, in the order of 6 cycles per second tremolo oscillator38- to suitable phase split circuitry 40, phase shift circuitry 41, andphase split circuitry 42 such that four drive voltages phase shifted inthe order of zero, 90, 180 and 270 are provided on the respective lines43, 44, 45 and 46. A suitable oscillator control 48 for example avoltage regulator may be employed to regulate the precise tremolo rate.

From the description thus far, it will be understood that lamps 25, 26,2'7 and 28 will light sequentially at a tremolo rate and theirrespective illuminations will be displaced in phase. This sequentialphasing of lamps 25, 26, 27 and 28 will in turn cause tubes 20, 21, 22and 23 to be sequentially illuminated and such illumination phasedisplaced in a like manner. Thus, any audio signal coming out of tonegenerator-amplifier will be sequentially directed at a tremolo rate tothe speakers 1, 2, 3 and 4 and in the same order. For this reason, thesource of sound coming out of the area Where speakers 1, 2, 3 and 4 arelocated will seem to rotate smoothly from speaker 1 to speaker 2, tospeaker 3, to speaker 4, back to speaker I and so forth.

Organ tone generator-amplifier 10 is of course simply representative ofone of the several similar tone generators to be found in the typicalelectric organ and which by voicing circuitry, not shown, areselectively connected to the audio circuits to be heard. Thus, any tonegenerator could be connected into the circuitry of FIGURE 1 and its tonemade to assume a rotating tremolo effect in the manner just described.

While those skilled in the art will appreciate the many possible ways ofderiving the required number of phase shifted voltages from tremolooscillator 38, one circuit is illustrated in more detail in FIGURE 2 inwhich the respective phase split, phase shift and driver circuits ofFIGURE 1 are boxed in dashed lines bearing the same identifyingnumerals. Before proceeding to the details of FIGURE 2 however,reference is made to FIGURE 3, which is later discussed, to indicate avery generalized representation of the invention and the fact thatmagnetic, heat, pressure and other kinds of sensitive devices might beemployed in place of tubes 20, 21, 22 and 23.

In FIGURE 2, the 90 phase shift circuit 41 is coupled through acapacitor 60 to tremolo oscillator 38 and includes for phase shiftingpurposes capacitors 61, 62 and resistors 63, 64 and 65. A furthercoupling capacitor 70 connects phase shift circuit 41 to phase splitcircuit 42 made up of resistors 71, 72, 73 and 74 and transistor 75connected as shown. Resistors 73 and 74 should be equal in value. Asindicated in FIGURE 2, a 90 shifted voltage wave arriving on line 76from phase shift circuit 41 results, with properly chosen values, in twovoltage waves shifted respectively to 90 and 270 on lines 77 and 78.Since phase shifting and operation of such circuitry is well understoodand is not claimed, per se, its specific operation is not dealt with infurther detail. Other phase arrangements may also be employed. Forexample, circuitry could be provided to shift plus 45 on one line andminus 45 on another line and each of these phase split to obtain fourvoltages successively shifted 90 apart.

The output on line 78 connects through coupling capacitor 80 to the lampdriver 33 which drives lamp 28 through line 81. As illustrated, typicaldriving circuitry is employed in drivers 30, 31, 32 and 33 and in thephase split circuit 40. The zero or reference phase voltage derived fromphase split circuit 40 is fed on line 82 to driver 30 and through line83 there is developed the corresponding zero phase driving voltageacross lamp 25. Similarly, line 84 carries the 180 phase voltage throughcoupling capacitor 85 to driver 32 such that there is developed in line86 the corresponding 180 phase driving voltage across lamp 27. In asimilar manner of developing voltage and phase, line 87 carries the 90voltage to lamp 26.

Considering particularly the driver circuit 33 and certain aspects ofits operation, the ratio of resistors 34 and 35 determines both the ACand DC voltage across lamp 28 with respect to voltage applied at point36. The ratio of resistors 37 and 47 determines both the AC and DCvoltage across lamp 28 with respect to voltage applied at point 36, theratio of resistors 37 and 47 determines the bias on the NPN transistor52 and in conjunction with resistors 34 and 35 determines the referencevoltage applied to point 53. In place of the type of resistor-capacitornetwork comprising capacitor 80 and resistor 37 and 47 for developingthe voltage at point 36, point 54 is used as a reference level to supplybias voltage for transistor 55 at point 56.

Considering the operation of the circuitry and system illustrated inFIGURES 1, 2 and 3, it will be seen that the voltages which energizelamps 25, 26, 27 and 28 are successively out of phase by 90.Accordingly, the time of occurrence of minimum impedance or resistancein tubes 2%), 21, 22 and 23 is successively out of phase by 90 timeintervals. That is, if the tremolo oscillator is running precisely at 6cycles per second each 90 phase interval represents a time of onetwenty-fourth of a second (V second). In this example, the maximumbrightness of the lamps 25-28 will be successively phased A second apartand the time of minimum impedance in tubes 20-23 will be successivelyphased second apart. As indicated by the drawings, each lamp is biasedwith direct current (DC) voltage to overcome the two brightness maximacommon to an alternating current cycle. This DC bias also sets the levelof modulation. With such condition and with the organ tonegenerator-amplifier in operation, it will be seen that the source ofmaximum sound intensity will sound as if it is moving from speaker I tospeaker 2 to speaker 3, to speaker 4 and back to speaker I at Ms secondper cycle intervals, this being a tremolo type sound effect.

With reference to the phasing of the impedance or resistance in tubes20, 21, 22 and 23, it is noted that it is preferable to achieve a truesinusoidal phasing. However, a periodic wave which in fact departssubstantially from a sinusoidal wave will give pleasing effects. Thedescribed rate of rotation can of course be controlled by the tremolooscillator control 48 since the lamp frequency or rate at which maximumlamp intensity moves from lamp to lamp (lamps 25-28) is controlled bycontrol 48. Accordingly, the rate at which minimum impedance moves fromtube to tube (tubes -23) is also controlled by control 48 which meansthat the rate of rotation of the sound originating in tonegenerator-amplifier 10 and coming from speakers 1, 2, 3 and 4 iscontrolled by control 4-8, the net effect being to introduce a ratecontrollable tremolo effect in the sound ultimately heard by thelistener.

In the prior co-pending application previously referred to the vibratooscillator 50' operates at the same frequency as the tremolo oscillator38 and is connected to the tone source (organ tone generator andamplifier 10) so as to subject the tone source to vibrato or frequencymodulation. The tone source in the prior application is not howeversimultaneously subjected to both tremolo and vibrato. In the presentinvention however it has been discovered that if the tone source issubjected to the same tremolo or amplitude modulation, preferably 6cycles per second, as is applied to the impedances (tubes 20, 21, 22,23) and is also subjected to a vibrato or frequency modulation operatingpreferably at twice the frequency of the tremolo modulation, i.e. 12cycles per second, and the vibrato is furthermore synchronized with thetremolo, a highly realistic Leslie effect is achieved.

In the drawings, it will be noted that vibrato oscillator 50, with anappropriate control 51 such as previously referred to, operates at 12cycles per second and is connected through a suitable synchronizingcircuit 66 to the tremolo oscillator 38 and is also connected to anadding circuit 67. Adding circuit 67 is also connected to receive theoutput of the tremolo oscillator 38 through a variable phase shiftcircuit 68 and the output of adding circuit 67 is connected through line69 to the tone source, the organ tone generator and amplifier 10.

By reason of having the organ tone generator-amplifier 10 modulatedsimultaneously by the added and synchronized outputs of the 12 cyclevibrato oscillator 50 and the 6 cycle tremolo oscillator 38 a relativelycomplex audio signal is fed out on line 79 and it is this complex signalwhich is rotated at the tremolo rate of oscillator 38 among the speakers1, 2, 3 and 4. Of special interest to the present invention is the factthat the human ear can detect almost no difference between a systemoperating according to the Leslie effect and a system operatingaccording to the present invention. While the system disclosed in thereferred to co-pending application also gave a similar effect thepresent circuit is even superior in the quality of the effect. Dependingon the precise sound effect desired, the system of the present inventionoffers a number of variables including the physical location of thespeakers, the exact tremolo and vibrato frequency values and the phasedisplacement of the tremolo and vibrato frequencies. With regard tophase displacement a wide latitude is available by reason of the phaseshift circuit 68 and such a shifting arrangement also provides a meansfor compensating for any drift away from some desired phase difference.

As with the circuit of the referred to co-pending application, severaldistinctions will be noticed between the present invention and the usualLeslie system. In particular the present invention has no physicallymoving parts and no mechanical, inertia or mechanical wear problems.Additionally, the tremolo and vibrato components are individually andindependently controllable in the present invention as to individual andrelative frequencies and phases whereas such components become mixed inthe conventional Leslie system without any form of independent controlor regulation being available. Another aspect of the present inventionis to be seen in the fact that the lamp-photoconductor tube arrangementeffectively isolates the audio from the tremolo control circuit.Consequently extraneous noise in the control circuitry which might arisein the tremolo oscillator, phase shift, phase split or lamp drivercircuits is not introduced into the audio. It can also be seen thatsound patterns can be controlled by positioning the speakers andmodifying the speakers as desired. Only one amplifier is required andwithout the complexity of a rotating speaker system, proper attentioncan be paid to the speaker baffling and loading so that greatly extendedfrequency response and power handling capabilities can be obtained.

FIGURE 3 illustrates the invention in a somewhat more general sense asapplied to simulated sound rotation. As previously mentioned, tubes 20,21, 22 and 23 may be looked upon simply as being sensitive devices andlamps 25, 26, 27 and 28 and their associated phasing and drive means maybe looked upon as sequential impedance phasing means compatible with thecharacter of the lamps sensitivities. Thus, other sensitive" devicessuch as magnetic, heat, pressure and the like may be employed withcompatible sequential impedance phasing means.

Asillustrated in FIGURE 3, the present invention as applied in broadterms to moving sound source simulation may be reduced to a basic systememploying the same plurality of speakers 1, 2, 3 and 4 connected inparallel to the tone generator and amplifier 10 and a plurality ofsensitive devices or variable impedances, one for each speaker, 137,138, 139 and 140. A control means 141 labeled sequential impedancephasing control which is compatible with the character of the impedancesmay be employed to sequentially and smoothly vary the values of theimpedances in some predetermined order and phase and at somepredetermined frequency such that there is a smooth transistionalrotation from speaker to speaker. Other components previously describedare connected into the generalized circuit as shown in FIGURE 3. Controlmeans 141 may of course take many forms and the lamp, lamp driver andphase control illustrated in the drawings all refer to a light sensitivetype system whereas a comparable system following the invention might bebased on magnetic, heat, pressure or other form of sensitivity and stillrealize the unique sequential keying and rotative character of theinvention.

Thus, while a specific embodiment of the invention has been described,it will be apparent that various modifications may be made withoutdeparting from the spirit and scope of the invention as set forth in theclaims.

What is claimed is:

1. In an electric musical instrument including a tone generator; meansto simultaneously amplitude and frequency modulate said tone generatorat respective modulating frequencies in the order of six and twelvecycles per second; a plurality of speakers each having an electricalconnection to said generator; a plurality of light sensitive impedances,one for each speaker connection and effective when illuminated to makesuch connection and when not illuminated to block such connection; aplurality of light sources, one for each impedance and effective whenenergized to illuminate such impedance; a plurality of sources ofenergizing voltages, one for each light source, said voltage sourcesbeing productive of continuous periodic wave voltages of the samepredetermined frequency as said tone generator amplitude modulatingfrequency but sequentially stepped out of phase whereby to cause arepetitive sequential and smoothly varying energization of said lightsources and smoothly varying illumination of said imped'ances, saidspeakers thereby being sequentially connected to said generator in thesame sequential phase relation as said voltages and in the repetitiveorder in which the respective speaker connections are made to produce anaudible tone whose source rotates smoothly from speaker to speaker in acorresponding sequence and at said amplitude modulating frequency whilesaid tone is continuously modulated in both amplitude and frequency atsaid six and twelve cycles as said source moves.

2. In an electric musical instrument including a tone generator; meansto simultaneously both amplitude and frequency modulate said tonegenerator at respective modulating frequencies in the order of six andtwelve cycles; a plurality of speakers each having an electricalconnection to said generator; a plurality of light sensitive impedances,one for each speaker connection and effective when illuminated to makesuch connection and when not illuminated to block such connection; aplurality of light sources, one for each impedance and effective whenenergized to illuminate such impedance and voltage drive meansresponsive to said amplitude modulating frequency to sequentially andsmoothly energize said light sources in some predetermined order and atsaid amplitude modulating frequency whereby said connections aresequentially made at said amplitude modulating frequency incorresponding order, and tone from said generator is made to sound as ifits source were moving smoothly from speaker to speaker in acorresponding sequence while being both amplitude and frequencymodulated at said respective six and twelve cycle frequencies duringsuch moving.

3. In an electric musical instrument including a tone generator; aplurality of speakers each having an electrical connection to saidgenerator; a plurality of light sensitive impedances, one beingconnected in series for each speaker connection and effective whenilluminated to make such connection and when not illuminated to shiftand drive means being effective to provide on said outputs smoothlyvarying energizing voltages for said light sources, said voltages beingat said tremolo frequency but sequentially stepped out of phase wherebyto cause a repetitive smoothly varying sequential energization of saidlight source and illumination of said impedances, said speakers therebybeing sequentially and smoothly connected to said generator in the samesequential phase relation as said voltages and in the repetitive orderin which the respective speaker connections are made; a synchronizingcircuit connected to synchronize the output frequencies of said tremoloand vibrato oscillators; an adding circuit connected to modulate saidtone generator with the sum of the outputs of said tremolo and vibratooscillators; said tone generator thereby being effective toproduce anaudible tone whose source moves smoothly at said tremolo frequency fromspeaker to speaker in a sequence corresponding to said repetitive orderwhile said tone is simultaneously modulated both in amplitude andfrequency at said respective different frequencies.

4. In an electric musical instrument as claimed in claim 3 includingvariable phase shift means connected between said tremolo oscillator andsaid adding circuit thereby allowing the relative phases of said tremoloand vibrato oscillators to be shifted prior to modulation of said tonegenerator.

5. In an electric musical instrument including a tone generator; aplurality of physically displaced speakers connected in parallel to saidgenerator; a plurality of substantially identical impedances, one foreach speaker and connected in series between the speaker and said tonegenerator, said impedances each characterized by having a similarvariable impedance characteristic sensitive to a control means ofcorresponding character; a tremolo oscillator operative at a tremolofrequency in the order of six cycles per second; a vibrato oscillatoroperative at a vibrato frequency in the order of twelve cycles persecond; means connected to synchronize said oscillators and the outputsthereof and modulate therewith said tone generator; sequential impedancephasing control means of said corresponding character respective to saidtremolo oscillator and including means to smoothly and sequentially varythe values of said impedances in some predetermined order and phase andat said tremolo frequency, thereby to produce an audible tone whosesource moves smoothly at said tremolo frequency from speaker to speakerwhile said tone is simultaneously modulated by said different tremoloand vibrato frequencies.

No references cited.

ARTHUR GAUSS, Primary Examiner.

D. D. FORRER, Assistant Examiner.

3. IN AN ELECTRIC MUSICAL INSTRUMENT INCLUDING A TONE GENERATOR; APLURALITY OF SPEAKERS EACH HAVING AN ELECTRICAL CONNECTION TO SAIDGENERATOR; A PLURALITY OF LIGHT SENSITIVE IMPEDANCES, ONE BEINGCONNECTED IN SERIES FOR EACH SPEAKER CONNECTION AND EFFECTIVE WHENILLUMINATED TO MAKE SUCH CONNECTION AND WHEN NOT ILLUMINATED TO BLOCKSUCH CONNECTION; A PLURALITY OF LIGHT SOURCES, ONE FOR EACH IMPEDANCEAND EFFECTIVE WHEN ENERGIZED TO ILLUMINATE SAID IMPEDANCE; A TREMOLOOSCILLATOR SOURCE OPERATIVE AT A TREMOLO FREQUENCY IN THE ORDER OF SIXCYCLES PER SECOND; A VIBRATO OSCILLATOR SOURCE OPERATIVE AT A VIBRATOFREQUENCY IN THE ORDER OF TWELVE CYCLES PER SECOND; ELECTRICAL PHASESHIFT AND DRIVE MEANS CONNECTED TO SAID TREMOLO OSCILLATOR AND HAVING APLURALITY OF OUTPUTS, ONE FOR EACH OF SAID LIGHT SOURCES, SAIDELECTRICAL PHASE SHIFT AND DRIVE MEANS BEING EFFECTIVE TO PROVIDE ONSAID OUTPUTS SMOOTHLY VARYING ENERGIZING VOLTAGES FOR SAID LIGHTSOURCES, SAID VOLTAGES BEING AT SAID TREMOLO FREQUENCY BUT SEQUENTIALLYSTEPPED OUT OF PHASE WHEREBY TO CAUSE A REPETITIVE SMOOTHLY VARYINGSEQUENTIAL ENERGIZATION OF SAID LIGHT SOURCE AND ILLUMINATION OF SAIDIMPEDANCES, SAID SPEAKERS THEREBY BEING SEQUENTIALLY AND SMOOTHLYCONNECTED TO SAID GENERATOR IN THE SAME SEQUENTIAL PHASE RELATION ASSAID VOLTAGES AND IN THE REPETITIVE ORDER IN WHICH THE RESPECTIVESPEAKER CONNECTIONS ARE MADE; A SYNCHRONIZING CIRCUIT CONNECTED TOSYNCHRONIZE THE OUTPUT FREQUENCIES OF SAID TREMOLO AND VIBRATOOSCILLATORS; AN ADDING CIRCUIT CONNECTED TO MODULATE SAID TONE GENERATORWITH THE SUM OF THE OUTPUTS OF SAID TREMOLO AND VIBRATO OSCILLATORS;SAID TONE GENERATOR THEREBY BEING EFFECTIVE TO PRODUCE AN AUDIBLE TONEWHOSE SOURCE MOVES SMOOTHLY AT SAID TREMOLO FREQUENCY FROM SPEAKER TOSPEAKER IN A SEQUENCE CORRESPONDING TO SAID REPETITIVE ORDER WHILE SAIDTONE IS SIMULTANEOUSLY MODULATED BOTH IN AMPLITUDE AND FREQUENCY AT SAIDRESPECTIVE DIFFERENT FREQUENCIES.